No persistent changes in pasture vegetation or seed bank composition after fallowing
The practice of fallowing pastures during the growing season is intended to increase plant diversity and allow natural reseeding of forage grasses. Fallowing delivers these benefits in New Zealand, but has been adopted on rotationally stocked farms in the northeastern United States with little or no quantitative assessment. Allowing the pasture to remain ungrazed may allow weedy species to produce seeds, and could reduce legume populations. We measured the seed bank composition (n = 23) and aboveground vegetation (n = 32) in paddocks that had been fallowed from 0–6 yr previously on an organic dairy in Maryland. Transect sampling was used to characterize the canopy cover of the dominant species three times per year for 3 yr. Germinable seed was identified from 5-cm soil cores collected in the spring and autumn in 2 yr. Fallowing did not produce any changes that persisted for more than 2 yr in either the seed bank or the vegetation of this farm. Tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] and other pasture grasses set seed, increasing in the seed bank during the fallow year, but this did not produce long-term changes in either the seed bank or the vegetation. The proportion of weedy forbs in the seed bank increased, and the legume cover decreased, but only temporarily. Natural reseeding of tall fescue promoted by fallowing did not cause changes in the vegetation, but could lead to increased endophyte infestation in the endophyte-free tall fescue originally planted.